Monday, January 23, 2017

The double slit with a twist: an important quantum experiment?

Just browsing through arXiv, as you do when there is not much on TV, and found a paper from last week by a group of Chinese researchers which sounds very significant.  Here's the abstract:
Are quantum states real? How to think about this the most important, most fundamental and most profound question in quantum mechanics still has not been satisfactorily resolved, although its realistic interpretation seems to have been rejected by various delayed-choice experiments. The heart of the matter comes down to what can describe physical reality if wavefunctions cannot. Here, to address this long-standing issue, we present a quantum twisted double-slit experiment, in which orbital angular momentum degree-of-freedom is employed to 'mark' the double slits (mimicked by spatial light modulators). Besides providing a which-slit observation interface, by exploiting the variable arrival time ascribed to the subluminal feature of twisted photons, the behavior of a photon during its time in flight is revealed for the first time. We found that the arrival time of photons does not accord with the states obtained in measurements, but agree well with the theoretical predictions calculated from their wavefunctions during the propagation. Our results demonstrate that wavefunctions describes a realistic manner of quantum entities' existence and evolution rather than only a mathematical abstraction for only providing a probability list of measurement outcomes. This finding makes an important update in understanding the role of wavefunctions in the evolution of quantum entities, inspires a new insight on nonlocality and wave-particle duality, and reminds us there is a neglected powerful resource for quantum science needing revisit.
As is common in such papers, the introduction and (this time) even the conclusion are fairly comprehensible, and you don't have to follow the maths in between.  Here's their surprising conclusion:

The cartoon they refer to is this:

I'm guessing that there might be a dispute over their interpretation of their experiment, but we'll see.  I'd be a bit surprised if this doesn't make it into science journalism soon...

No comments: